Method for operating a motor-driven vehicle

ABSTRACT

1. Method for operating a motor-driven vehicle.  
     2.1 Proposed is a simple and cost-effective method, which enables a safe operation of the motor vehicle comprising an electrical braking system with a parking brake.  
     2.2 To avoid damages of the braking system of the motor vehicle due to driving with an applied parking brake, the parking brake is automatically released, if the speed of the motor vehicle exceeds a prescribed minimum value and additionally the drive unit of the motor vehicle is driven in a specific operating state and additionally at least one operating element of the motor vehicle that is to be actuated by the operator of the motor vehicle is being or has been actuated by the operator.

[0001] The invention relates to a method according to the preamble of the Patent Claim 1 as it is known from the DE 198 14 657 A1.

[0002] In motor-driven vehicles, a parking brake is generally provided for arresting or fixing the motor vehicle at a standstill and especially in connection with the parking of the motor vehicle. When again beginning to drive the motor vehicle, the releasing of the set parking brake can be forgotten by the operator of the motor vehicle; the driving with a set or applied parking brake can, however, lead to an impairment or damage of the braking system of the motor vehicle. As a result, driving with a set or applied parking brake should be avoided.

[0003] From the initially mentioned DE 198 14 657 A1 with a control and/or regulating arrangement for an electrical parking brake arrangement of motor vehicles, forming the general background of this art, it is known to provide a sensor unit for measuring the wheel rotational speed of the vehicle, by means of which the two driving conditions, standstill or parking and driving, of the vehicle can be recognized. With this information by itself, a driving of the motor vehicle is often erroneously assumed, even in connection with an undesired and unintended rolling of the vehicle (for example due to diminishing or slackening braking force or insufficient setting or applying of the parking brake), whereby critical situations impairing the safety can arise.

[0004] The underlying object of the invention is to propose a simple method for operating a motor-driven motor vehicle with a high reliability and safety.

[0005] This object is achieved according to the invention by the features in the characterizing portion of the patent claim 1. Advantageous embodiments of the method are the subject of the further patent claims.

[0006] The (electrical) parking brake is deactivated upon the presence of a desired driving state or mode of the motor vehicle, that is to say, the parking brake is automatically released when, on the one hand, a movement or motion of the motor vehicle exists, and on the other hand, the movement or motion of the motor vehicle was intended and willfully initiated by the operator of the motor vehicle. Especially, the exceeding of a specific minimum speed is defined as the motion or movement of the motor vehicle (for example the exceeding of a speed of 1.5 km/h), and the driving of the drive unit of the motor vehicle in a specific operating state or mode and the actuation of at least one operating element of the motor vehicle that is to be actuated by the operator of the motor vehicle are defined as an unambiguous recognizable desire of the operator for the movement of the motor vehicle (for beginning to drive or driving away). As the operating state or mode of the drive unit of the motor vehicle, especially, the motor of the motor vehicle must be running and/or the transmission must be connected with the motor, that is to say as a result of a corresponding actuation of the gear shift lever of a manual shift transmission or of the selector lever of an automatic transmission, a gear must have been engaged by the operator. Especially the driving pedal (gas pedal) is utilized as the operating element of the motor vehicle that is to be actuated by the operator of the motor vehicle, that is to say the driving pedal (gas pedal) must have been stepped on by the operator of the motor vehicle to move it through a specific distance and/or the clutch pedal, that is to say the clutch pedal may not be stepped on all the way down (it must be coupled-in, the clutch must be released), thus a force flow must exist from the motor via the drive train to the wheels of the motor vehicle; optionally, the safety belt can be additionally utilized as the operating element of the motor vehicle that is to be actuated, that is to say the safety belt must be put on or must have been put on by the operator of the motor vehicle. With the aid of plausibility considerations, at least one of these criteria is evaluated, and from this a determination is made with respect to the driver's desire for the movement of the motor vehicle (for driving away or beginning to drive the motor vehicle). The movement of the motor vehicle can be determined, for example, by means of sensors for detecting the speed and/or the acceleration of the motor vehicle, for example by means of wheel rotational speed sensors and/or acceleration sensors or via an optical path distance measurement or via the transmission of the motor vehicle; the operating states or modes of the drive unit of the motor vehicle signaling the operator's desire for movement of the motor vehicle, and the actuations of the operating elements of the motor vehicle that are to be actuated can be determined from specific data of the motor vehicle that are characteristic thereof, and can be obtained from the measured values of suitable sensors, for example from the measured values of sensors for detecting the position of the driving pedal (gas pedal), from sensors for detecting the position of the gear shift lever or the selector lever (selector lever sensors), and sensors for detecting the operating state of the motor (for example rotational speed sensors for detecting the rotational speed of the motor and/or rotational moment or torque sensors for detecting the rotational moment or torque of the motor).

[0007] The basic informations underlying the method can be obtained in a simple manner, especially by means of sensors already present in the motor vehicle, so that driving with a set or applied parking brake can advantageously be prevented in a simple and cost-effective or economical manner, without the operator of the motor vehicle having to be bothered by or pay attention to this, and without the parking brake being unintentionally released. Thereby, a method that increases the safety in the driving traffic can thus be realized.

[0008] In connection with the drawing, the invention shall be explained in further detail, whereby a schematic block circuit diagram for carrying out the method is shown in the FIGURE.

[0009] According to the FIGURE, a control unit 1 (logic unit) is provided in the motor vehicle, to which control unit 1, sensor signals SS1, SS2, SS3, SS4, SS5 of plural sensors 3, 4, 5, 6, 7 (that is to say the measured values acquired from the sensors 3, 4, 5, 6, 7) are delivered as input signals, and which, dependent on the sensor signals SS1, SS2, SS3, SS4, SS5, actuates the electrical braking system 2 of the motor vehicle with an output signal AS (control signal) generated therefrom (for example by acting on the brake actuator for prescribing a specific braking force). The sensor signals SS1, SS2, SS3, SS4, SS5 provide, as measured values, information on the one hand regarding the motion of the motor vehicle (and especially also regarding the speed of the motor vehicle in the motion), on the other hand regarding the desire of the operator of the motor vehicle (the driver's desire) for movement of the motor vehicle. As a sensor for detecting the motion of the motor vehicle, for example, at each wheel of the motor vehicle, a wheel rotational speed sensor 3 is provided, of which the sensor signals SS1 are utilized as a measure for the speed of the motor vehicle. As sensors for detecting the desire of the operator for the movement of the motor vehicle, there are provided, for example, a travel or displacement sensor 4 (sensor signal SS2) detecting the position of the gas pedal (driving pedal), a selector lever sensor 5 (sensor signal SS3) detecting the position of the gear shift lever, a rotational speed sensor 6 (sensor signal SS4) detecting the operating state of the motor (the motor data) by the detection of the motor rotational speed, and a clutch sensor 7 (sensor signal SS5) detecting the state of the clutch pedal. The sensor signals SS1, SS2, SS3, SS4, SS5 of the sensors 3, 4, 5, 6, 7 and therewith the measured values thereof are evaluated by the control unit 1 (logic unit); the control unit 1 (logic unit) is arranged in the interior area or the exterior area of the motor vehicle and, for example, integrated in a control device of the motor vehicle, for example, in a control device arranged on the rear axle of the motor vehicle. In the evaluation, it is especially monitored or checked by the control unit 1 (logic unit), whether the speed of the motor vehicle exceeds a specific minimum speed of, for example, 1.5 km/h, whether the gas pedal (driving pedal) is being actuated by the operator of the motor vehicle, whether a gear is engaged, whether the clutch pedal is actuated (whether it is being clutched-in or clutched-out), and whether the motor of the motor vehicle is running. With the aid of plausibility considerations, at least one of these criteria is evaluated, and therefrom a determination is made with respect to the driver's desire for starting to drive the vehicle: if it is assumed that the driver desires to start driving the motor vehicle, then, independent of the momentary state of the (electrical) parking brake, it is deactivated by appropriate action on the brake actuator of the electrical brake system 2 by the output signal AS of the control unit 1 (logic unit), that is to say the (electrical) parking brake is released. 

1. Method for operating a motor-driven motor vehicle with an electrical braking system (2) comprising a parking brake, characterized in that the parking brake is automatically released upon the existence of the following conditions: a) the speed of the motor vehicle exceeds a prescribed minimum value, b) the drive unit of the motor vehicle is operated in a specific operating state, c) at least one operating element of the motor vehicle to be actuated by the operator of the motor vehicle is being or has been actuated by the operator.
 2. Method according to claim 1, characterized in that the drive unit of the motor vehicle must be driven with a running motor.
 3. Method according to claim 1 or 2, characterized in that a force flow from the motor via the drive train to the wheels of the motor vehicle must be present.
 4. Method according to claim 3, characterized in that a gear shift lever or selector lever must be engaged and the clutch must be released.
 5. Method according to one of the claims 1 to 4, characterized in that, the driving pedal must be actuated as the operating element of the motor vehicle to be actuated by the operator of the motor vehicle.
 6. Method according to one of the claims 1 to 5, characterized in that, the safety belt must be put on as the operating element of the motor vehicle to be actuated by the operator of the motor vehicle.
 7. Method according to one of the claims 1 to 6, characterized in that the speed of the motor vehicle is detected via wheel rotational speed sensors (3).
 8. Method according to one of the claims 1 to 7, characterized in that the operating state of the motor is detected via rotational speed sensors (6).
 9. Method according to one of the claims 1 to 8, characterized in that the position of the gear shift lever or selector lever of the motor vehicle is detected via selector lever sensors (5) connected with the shifting linkage or the transmission. 